If you lease out a property and the tenant has some work done to fix up his office for his own use...?

and he does not pay for the work that was done, can the worker he hired put a lein on my property?

The law varies by state, but generally yes.

I have seen notices posted at some worksites saying that the landlord is notifying the company doing the work that the landlord is aware of the work and is not responsible for it and has filed a copy at the courthouse or some other government place. I assume that if you go through this procedure (which will vary slightly from state to state) then no, but if you allow the work to go on without following this procedure, then yes. I do not know what happens if you are unaware of the work.

Again, you have to find out the exact procedure for your particular state; doing what I have summarized is not enough.

First..you should get a copy of the work agreement and see whose name is on it to pay for the work. If your tenant signed for you..get a lawyer and take him to the cleaners. You may also be able to raise his rent to help pay for this work done. I find this story deplorable and he should have talked to you first before doing anything on his own. Also, look over your lease you made with him and see if you made stipulations that any remodeling is ok or not and what the stipulations were for such work.